Two other types of lettuce produced in the Lower Colorado River region near Yuma, Arizona, are Boston and leaf lettuce. Reporting on acreage and economic value does not distinguish between lettuce types, but the land area cropped to these lettuce types is much smaller than iceberg and romaine lettuce. 

Like the other lettuce types, stands are often established by solid set sprinklers and receive furrow irrigation for all subsequent irrigation. However, in some situations these two lettuce types are irrigated by sprinklers all season. These two lettuce types have similar growth periods and water use characteristics and our presentation for these two crops were combined. 

Using eddy covariance (Figure 1), we have measured seasonal ETc from 184.5 to 212.5 mm (7.3 to 8.4 acre-inches). Like the other cool season crops days from first irrigation to harvest vary, growth and water use are more accurately tracked using growing degree days and satellite imagery. The calculated crop coefficients by growing period are shown in Table 1. As for most cool season vegetable crops at Yuma, irrigation efficiencies are high in-season and salinity increases. An off-season pre-irrigation is usually required to restore salt balance.